Kevin covered the story in late April when rumors of the change in pricing and plans to block VoIP services surfaced. It turns out that TeliaSonera has tested the new pay for VoIP plans in Spain on its Yoigo subsidiary. Subscribers are charged EUR 6 ($7.50) per month for 100MB of VoIP traffic, which supports between five and ten hours of your Google Talk or Skype calling. Existing contract holders won’t have to pay such fees until their contracts run out and TeliaSonera will also offer unlimited plans where the cost of VoIP is included.

Carriers are clearly eager to hold onto their dying voice revenue, which in the U.S. comprises roughly 60 percent of what they make on average from each customer a month, according to data from the first quarter of 2012 gathered by Chetan Sharma. As you can see from the chart below, the revenue is declining along with revenue from texting. This is a global trend. When everything is IP-based, from voice to messaging services, carriers are stuck selling data — and data doesn’t carry the profit margins nor the limits of voice. A person can only talk so many minute per month, offering a ceiling on the potential outlay to support the service. But demand for data just grows and grows as we find new apps that can use it.

Still a charge for Skype provided VoIP — or VoIP provided by any other over-the-top provider — is a problem for fans of network neutrality who worry that TeliaSonera’s charges are an attempt to protect the carriers’ own business and services. Network neutrality is the principle that states ISPs can’t discriminate against the packets traveling over their networks. In this case, charging a user more to use an over-the-top VoIP offering could be construed as discriminating against those services.

However, given the revenue and margin pressure at operators, I doubt this is the last time we’ll see this issue arise in Europe or in other regions. In the U.S. network neutrality rules aren’t extended to wireless networks, but the FCC has said it would look askance at operators who try to discriminate against services that carriers also offer such as voice and messaging.